Roger Federer also believes that Andre Agassi enjoyed the sport more than he admitted. (AP)

Roger Federer, who continues to revel in his enjoyment of the game, says he's skeptical when other players claim they don't like tennis.

That includes Nick Kyrgios and Bernard Tomic, who both expressed a lack of desire at times, along Andre Agassi, who in his autobiography he talks about hating the game during his career, even though he played for longer than most of his rivals. Kyrgios and Tomic have been frequently criticized in Australia for their ambivalence towards the sport.

"Yeah, I don’t think every day that’s true. I believe they do enjoy their time on the courts sometimes," Federer told the Sunday Times of Perth. "Agassi said the same after he retired and he played for 20-something years. I don’t believe him as well, everything that he said in that book.

"I do believe for the most part, deep inside of them, somehow they do enjoy their time. And there is moments when they do win a match, or there is moments in practice where they actually do enjoy it."

Federer, who says he is still motivated despite nearly 20 years on tour, added that Kyrgios and Tomic could benefit from concentrating more on the positives.

"Maybe there is moments when things are difficult. When you’re packing up the bags and traveling to the next event, or whatever it is. Then it becomes tricky sometimes. But that’s the case for everybody," said Federer. "But it’s also a question of seeing the glass half-full rather than empty. They still have some potential to fulfill. They know that and it’s a question up to them if they want to do it or not."

Federer is competing at this week's Hopman Cup mixed team competition.